Brace yourselves. That’s the message coming from leaders in Europe, Britain and Canada as autumn arrives, bringing with it crisp air and predictions of a dark pandemic winter.

Europe faces a “decisive moment.” Britain is at a “perilous turning point.” Canadians probably shouldn’t gather for Thanksgiving next month.

Leaders are emphasizing the risks ahead for countries heading into cooler months with case counts now growing again, not shrinking, and populations already fed up with pandemic restrictions.

They’re highlighting the deadly seriousness of a disease that has killed nearly 1 million people worldwide in the first nine months of this year — and is expected to kill many more.

And they’re offering a sharp contrast to President Trump, who has sought to play down the severity of the U.S. outbreak, which is the worst in the world.

Experts long predicted that a summer respite from strict coronavirus measures, plus the return to schools and offices, would lead to more covid-19 cases come fall. Now fall is here, and cases are rising — fast.

There’s little doubt they’ll climb further as the weather gets colder, activities move indoors, and the cold and flu season hits. Leaders see a limited window to blunt the force of the next wave.

“It is only September,” said Isaac Bogoch, an infectious-disease specialist at Toronto General Hospital. “If you live in the northern hemisphere, there is a long fall and winter ahead.”

There isn’t much mystery as to why cases are climbing — or why it’s happening now. After a brutal spring, many countries relaxed coronavirus restrictions through June, July and August, allowing citizens some simple pleasures: visits with family, a drink at the pub, even parties for some.

Then in late August and September, children in many countries started returning to school, allowing more parents to return to offices.

It’s clear that the return to semi-normalcy has exacted a cost. The fear is that community transmission will continue, leading to a surge in hospitalizations and deaths.

Top European officials have been issuing dire warnings about the wave of new cases engulfing many countries.

“We are at a decisive moment,” Stella Kyriakides, the European Union’s top official for health issues, said Thursday.

“Everyone has to act decisively,” she said. “It might be our last chance to prevent a repeat of last spring.”

The World Health Organization is delivering a similar message. Hans Kluge, the WHO’s regional director for Europe, described the situation as “very serious.”

Kluge told reporters last week that half of European countries had reported increases in cases of more than 10 percent in the past two weeks. In seven countries, they had doubled.

France is on high alert.

Prime Minister Jean Castex last week spoke of a “clear deterioration of the situation.”

On Wednesday, the French health ministry imposed new restrictions to curb what epidemiologists are calling a “second wave” and to ease the load on hospitals. In certain urban areas, including Paris, group sizes will now be limited, and bars will be required to stop serving after 10 p.m.

But the government has shied away from imposing another nationwide lockdown, after a strict shutdown from mid-March to mid-May.

In Britain, the mood has shifted from optimism to alarm.

This month, Prime Minister Boris Johnson said he was hopeful that some aspects of ordinary life would be “back to normal by Christmas” thanks in part to “Operation Moonshot,” the government’s plan to test 10 million Brits every day.

But on Monday, Patrick Vallance, the British government’s chief scientific adviser, and Chris Whitty, chief medical officer for England, said cases were doubling roughly every seven days. If that rate holds, they warned, there could be 50,000 per day by mid-October.

The next day, Johnson unveiled a package of new restrictions he said could be in place for six months.

In a televised address, he explained the need: “As in Spain and France and many other countries, we have reached a perilous turning point.”

Pubs and restaurants will now be required to close by 10 p.m. Masks will be mandatory for certain types of workers, including taxi drivers, retail workers and bar and restaurant staff.

“Now is the time for us all to summon the discipline and the resolve and the spirit of togetherness that will carry us through,” Johnson said.

In Canada, where the weather is already turning, the situation is also worrying.

A spike in cases in the country’s four largest provinces has reversed gains made during the late spring and early summer.

Public health officials say most of the new cases are concentrated in adults aged 20 to 39, but it’s only a matter of time before the novel coronavirus spreads to people at greater risk.

Hospitalizations, a lagging indicator of infections, are slowly climbing. Some testing centers in Ontario have been so overwhelmed that they have reached capacity and had to turn people away before even opening.

If the country continues on its current path, public health officials say, it will reach 5,000 cases a day by late October — more than at the height of its spring wave.

As in Europe, officials so far have opted for smaller and more targeted localized restrictions, keen to avoid another widespread shutdown.

Prime Minister Justin Trudeau stressed that people needed to change their behavior to avert a winter lockdown — and save the holiday season. Thanksgiving — Oct. 12 in Canada — is probably a wash, he said in a nationally televised address Wednesday. But depending on how Canadians respond now, they might “have a shot” at Christmas.

“The second wave isn’t just starting,” he said. “It’s already underway.”

Michael Birnbaum in Riga, Latvia, Karla Adam in London, James McAuley in Paris and Amanda Coletta in Toronto contributed to this report.